1. Field of the Invention
The present invention relates to the field of disc players capable of selecting and playing, on command, any of a plurality of stored discs and, more particularly, to autochanger type disc players suitable for optical compact discs (CDs).
2. Description of Related Art
Recently, in the field of audio equipment, digital audio playback systems utilizing pulse code modulation (PCM) technology to play back sound as faithfully as possible have been developed. Of these systems, playback systems employing CDs have become especially popular.
The CD conventionally used in a digital audio disc playback system is made from a transparent resin and has a diameter of approximately 12 cm and a thickness of approximately 1.2 mm. The CD has a thin metal film deposited on at least one disc surface, and pits or depressions are formed in the thin metal film. The pits or depressions produce light reflectivities that are different from the reflectivity of the non pitted portions of the metal film and that correspond to 1 or 0 of digitized data. When a signal is read out from a CD, an optical pickup incorporating a semiconductor laser or photoelectric transducing device tracks the information storage area of the CD radially from the center portions toward the outer portions, while the disc is rotated at a variable rotation speed between 200 and 500 rpm to achieve a constant linear velocity at all pickup points.
A CD stores such a large quantity of information that a single side can provide approximately one hour of stereophonic music. A CD is far superior to a conventional analog phonograph record in both sound quality and information storage density.
In view of the excellent characteristics of the CD, it has been suggested to use CDs in automatic multi-disc playback systems for business use, for example, in jukeboxes. It is possible to achieve such a system by using a conventional autochanger type disc player with CDs. Known autochanger type disc players, however, are complex in structure and bulky, partially because they have been designed for use with analog phonograph records. Therefore, the conventional disc players present control problems Another problem is the long time it takes to exchange one disc for another in a conventional disc player. In addition, a pusher-type mechanism normally has been used to move a disc from storage to a playing position. The pusher mechanism passes through the stack of discs, requiring the discs to be separated by relatively wide spaces to accommodate the bulk of the pusher mechanism. For these reasons, if the conventional autochanger type disc player is used with CDs without changing the essential structure of the disc player, numerous problems arise. Hence, the development of an autochanger type disc player suitable for CDs is a matter of intense commercial interest.
In view of the foregoing, the present invention is intended to provide an autochanger type disc player that makes possible an increase in the number of discs that can be accommodated. In addition, the autochanger promotes reliability of operation with a simple construction.
Furthermore, the present invention is intended to provide an autochanger type disc player that is capable of selecting with certainty a predetermined disc among many discs stored close to each other in a disc storage section, transferring the selected disc to a playback section without damaging the disc, and returning the disc to the disc storage section without damage.
Additional advantages of the present invention will be set forth in part in the description that follows and in part will be obvious from that description or can be learned by practice of the invention. The advantages of the invention can be realized and obtained by the apparatus particularly pointed out in the appended claims.